SIM800L — Quad-Band GSM / GPRS Cellular Module

Overview

The SIM800L is a miniature quad-band GSM/GPRS cellular transceiver module manufactured by SIMCom Wireless Solutions. It operates across 850/900/1800/1900 MHz frequencies to deliver SMS text messaging, voice calling, and GPRS mobile data packet connectivity for embedded IoT applications.

The module features a 3.7V–4.2V operating voltage range (tailored for direct 1S LiPo battery power), a Micro-SIM card slot, IPEX antenna connector, and standard AT command UART control interface.

Quick reference


Supply Voltage (`VCC`)	3.4 V to 4.4 V DC (4.0 V recommended, e.g. 1S LiPo or high-current LDO)
Peak Burst Current	Up to 2.0 A during GSM RF transmission bursts
Quad-Band Frequencies	GSM 850 / EGSM 900 / DCS 1800 / PCS 1900 MHz
UART Logic Level	2.8 V TTL (requires level shifter for 5V MCUs)
Default Baud Rate	Auto-baud / 115200 bps
SIM Card Socket	Micro-SIM (1.8V / 3.0V supported)
GPRS Data Rate	Download: 85.6 kbps / Upload: 85.6 kbps (Class 12)

Pinout

Standard Red SIM800L Breakout Header

Pin	Name	Type	Description
1	`NET`	Antenna / Net status	Connects to wire helical antenna / Network LED status output
2	`VCC`	Power Input	Supply voltage (+3.4 V to +4.4 V DC, MUST support 2A bursts)
3	`RST`	Digital Input	Active-LOW Reset input pin
4	`RXD`	Digital Input	UART Receive line (2.8V logic level input)
5	`TXD`	Digital Output	UART Transmit line (2.8V logic level output)
6	`GND`	Power	Ground (0 V)
7	`RING`	Digital Output	Ring Indicator line (pulls LOW on incoming call or SMS)
8	`DTR`	Digital Input	Sleep Mode control pin (`HIGH` = Enable Sleep mode)
9	`MIC+`, `MIC-`	Audio Input	Electret Microphone differential inputs
10	`SPK+`, `SPK-`	Audio Output	8 Ω Speaker differential outputs

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Operating Voltage	$V_{BAT}$	3.4	4.0	4.4	V	DC
Peak Transmit Current	$I_{PEAK}$	—	2.0	2.5	A	GSM RF burst transmission
Idle Current	$I_{IDLE}$	—	7.0	—	mA	Registered to network
Sleep Current	$I_{SLEEP}$	—	0.7	1.0	mA	Sleep mode ( $DTR = HIGH$ )
Transmit Power (Class 4)	$P_{TX900}$	—	2.0	—	W	33 dBm @ 850/900 MHz
Transmit Power (Class 1)	$P_{TX1800}$	—	1.0	—	W	30 dBm @ 1800/1900 MHz

AT Command Set Examples

Set terminal to 115200 baud with \r\n (CRLF) line endings:

Command	Expected Response	Description
`AT`	`OK`	Test module UART connection
`AT+CPIN?`	`+CPIN: READY`	Check if SIM card is inserted and unlocked
`AT+CSQ`	`+CSQ: 22,0`	Check signal strength (First number $> 10$ is good signal)
`AT+CREG?`	`+CREG: 0,1`	Check cellular registration (`0,1` = Registered home network)
`AT+CMGF=1`	`OK`	Set SMS text mode
`AT+CMGS="+1234567890"`	`>`	Send SMS (type body, end with `Ctrl+Z` / `0x1A`)
`ATD+1234567890;`	`OK`	Place voice call

Wiring

SIM800L Breakout Pin	Power Supply / Microcontroller	Notes
`VCC`	External 4.0V / 2A Power Source (LM2596 buck or 1S LiPo)	Do NOT power from Arduino 5V / 3.3V pins!
`GND`	Common `GND` (Power GND + MCU GND)	Must share ground
`TXD`	`RX` (e.g. GPIO16 on ESP32 / D2 on Arduino)	2.8V TTL output
`RXD`	`TX` (e.g. GPIO17 on ESP32 / D3 on Arduino)	Use 1kΩ/2kΩ voltage divider from 5V MCU

Warning

Critical Power Supply Requirement & Voltage Warning:

Voltage Window: The SIM800L operating voltage range is strictly 3.4 V to 4.4 V. Feeding 5.0 V directly to VCC will destroy the SIM800L chip! Supplying $<3.4\text{ V}$ causes brownout resets.
Peak Current: The module demands up to 2.0 A bursts during network transmission. If powered from an inadequate supply, the module will repeatedly reboot (LED blinks rapidly once per second continuously). Place a $1000\text{ }\mu\text{F}$ low-ESR electrolytic capacitor across VCC and GND.

Common mistakes

Powering from Arduino 5V or 3.3V pins: Microcontroller onboard regulators cannot supply 2.0 A current bursts, causing infinite reboot loops.
2G Network Availability: SIM800L is a 2G-only module. In countries where 2G networks have been decommissioned (e.g. USA, Australia), 2G modules cannot register on cellular towers. Use LTE Cat-M1 / NB-IoT modules (e.g. SIM7000G / SIM7600) instead.
Forgetting common ground: MCU and external power supply grounds MUST be connected together.

Notes

Network LED status: Blinking every 1s = Searching for network; Blinking every 3s = Registered on network.

Interface	UART, SIM Card, Speaker, Microphone, Antenna
Supply	3.4–4.4 V
Package	88-pin LGA (15.8 x 17.8 x 2.4 mm) / Micro-SIM Breakout Board